It would be more helpful to have a preference option to 1) do nothing and let me select which project to make active, 2) activate the last opened project. I agree. Not activating the previously active project would be a better default.

This is the single most annoying thing that makes me want to die every time it happens. People complain about accidentally clicking the loop on and off but it's nothing compared to closing a project and forgetting you had another one loaded or even worse, it reverts to the 1 you didn't want. The sense of dread, the NOOO! as you await the load bar you had no desire to finish.

PLEASE STEINBERG REMOVE THE AUTO ACTIVATION OF UNDERLYING PROJECT.

Make it do nothing... we can then simply click the activation or x, of what ever we require.

Just want to quote a post I've written in another thread (hope it helps somehow):

"Yes, this is annoying but I use a workaround for this.
I always start Cubase/Nuendo with a blank project than open all other loaded projects that I’m actually working on. Whenever I close any project, I don't need to think about which will be activated next, the blank project gets activated automatically in a second, then I can choose which other loaded project I want to activate.
It always defaults to the first blank project.
This can save you a lot of time."